The NATO information system was also indirectly threatened in October 1998, when a Serbian group of hackers known as Black Hand penetrated a Kosovo Albanian web server and threatened to sabotage the Alliance's information system. The organisation temporarily closed all foreign access to its web server and its web site was down for two days. Realising that the electronic defences of the NATO web server were extremely weak, experts took some countermeasures, which proved to be insufficient in the light of subsequent events.
During the Kosovo crisis, hackers attacked the NATO web site, causing a line saturation of the server by using a "bombardment strategy". The organisation had to defend itself from macro viruses from FRY trying to corrupt its e-mail system, which was also being saturated by one individual sending 2,000 messages a day. These attacks were possible because NATO was using the same server for the e-mail system and its web-pages. When these tasks are done by separate servers, as is now the case at NATO, the threat is reduced. Allied governments' web sites have also been targeted during the war, and according to US Air Force sources the attacks came not only from FRY, but also from Russia and China. It is unclear, however, whether these attacks were state-sponsored or the work of groups of hackers. Conversely, FRY's information systems were severely damaged by NATO bombings and electronic operations - although Belgrade itself dismantled communication systems to deprive its people of outside information.